SQLite

** The pager is used to access a database disk file.  It implements
** atomic commit and rollback through the use of a journal file that
** is separate from the database file.  The pager also implements file
** locking to prevent two processes from writing the same database
** file simultaneously, or one process from reading the database while
** another is writing.
**
** @(#) $Id: pager.c,v 1.321 2007/04/05 13:12:14 danielk1977 Exp $
*/
#ifndef SQLITE_OMIT_DISKIO
#include "sqliteInt.h"
#include "os.h"
#include "pager.h"
#include <assert.h>
#include <string.h>

**
** This routine may return SQLITE_IOERR, SQLITE_FULL or SQLITE_OK. It 
** does not set the pPager->errCode variable.
*/
static int pager_recycle(Pager *pPager, int syncOk, PgHdr **ppPg){
  PgHdr *pPg;
  *ppPg = 0;

  assert(!MEMDB);

  /* Find a page to recycle.  Try to locate a page that does not
  ** require us to do an fsync() on the journal.
  */
  pPg = pPager->pFirstSynced;

  /* If we could not find a page that does not require an fsync()

  assert( pPg->nRef==0 );

  /* Write the page to the database file if it is dirty.
  */
  if( pPg->dirty ){
    int rc;
    assert( pPg->needSync==0 );

    makeClean(pPg);
    pPg->dirty = 1;
    pPg->pDirty = 0;
    rc = pager_write_pagelist( pPg );
    if( rc!=SQLITE_OK ){
      return rc;
    }

  */
  for(i=0; i<=1; i++){

    /* Loop through all the SQLite pagers opened by the current thread. */
    for(p=pTsdro->pPager; p && (nReq<0 || nReleased<nReq); p=p->pNext){
      PgHdr *pPg;
      int rc;

#ifndef SQLITE_OMIT_MEMORYDB
      if( p->memDb ){
        continue;
      }
#endif

      /* For each pager, try to free as many pages as possible (without 
      ** calling fsync() if this is the first iteration of the outermost 
      ** loop).
      */
      while( SQLITE_OK==(rc = pager_recycle(p, i, &pPg)) && pPg) {
        /* We've found a page to free. At this point the page has been 

/*
** Allocate or recycle space for a single page.
*/
static int pagerAllocatePage(Pager *pPager, PgHdr **ppPg){
  int rc = SQLITE_OK;
  PgHdr *pPg;

  if( MEMDB || (!(pPager->pFirstSynced && pPager->pFirstSynced->pgno==0) && (
      pPager->nPage<pPager->mxPage || pPager->pFirst==0 || 
      (pPager->pFirstSynced==0 && pPager->doNotSync)
  )) ){
    /* Create a new page */
    if( pPager->nPage>=pPager->nHash ){
      pager_resize_hash_table(pPager,
         pPager->nHash<256 ? 256 : pPager->nHash*2);
      if( pPager->nHash==0 ){
        rc = SQLITE_NOMEM;
        goto pager_allocate_out;

#    May you share freely, never taking more than you give.
#
#***********************************************************************
#
# This file contains test cases focused on the two memory-management APIs, 
# sqlite3_soft_heap_limit() and sqlite3_release_memory().
#
# $Id: malloc5.test,v 1.9 2007/04/05 13:12:14 danielk1977 Exp $

#---------------------------------------------------------------------------
# NOTES ON EXPECTED BEHAVIOUR
#
#---------------------------------------------------------------------------

  execsql {
    SELECT count(*), sum(a), sum(b) FROM abc;
  }
} [list 20000 [expr int(20000.0 * 4999.5)] [expr int(20000.0 * 4999.5)]]

# Restore the soft heap limit.
sqlite3_soft_heap_limit $::soft_limit

# Test that there are no problems calling sqlite3_release_memory when
# there are open in-memory databases.
#
# At one point these tests would cause a seg-fault.
#
do_test malloc5-5.1 {
  db close
  sqlite3 db :memory:
  execsql {
    BEGIN;
    CREATE TABLE abc(a, b, c);
    INSERT INTO abc VALUES('abcdefghi', 1234567890, NULL);
    INSERT INTO abc SELECT * FROM abc;
    INSERT INTO abc SELECT * FROM abc;
    INSERT INTO abc SELECT * FROM abc;
    INSERT INTO abc SELECT * FROM abc;
    INSERT INTO abc SELECT * FROM abc;
    INSERT INTO abc SELECT * FROM abc;
    INSERT INTO abc SELECT * FROM abc;
  }
  sqlite3_release_memory
} 0
do_test malloc5-5.1 {
  sqlite3_soft_heap_limit 5000
  execsql {
    COMMIT;
    PRAGMA temp_store = memory;
    SELECT * FROM abc ORDER BY a;
  }
  expr 1
} {1}

sqlite3_soft_heap_limit $::soft_limit
finish_test
catch {db close}